The gains are small-scale, hard-won and in terms of territory overall don’t add up to much, in keeping with the incremental nature of war.

But after 3½ months of relentless airstrikes that have mostly targeted the Western-backed opposition to Assad’s rule, they have proved sufficient to push beyond doubt any likelihood that Assad will be removed from power by the nearly five-year-old revolt against his rule. The gains on the ground are also calling into question whether there can be meaningful negotiations to end a conflict Assad and his allies now seem convinced they can win.

“The situation on the ground in Syria is definitely not conducive to negotiations right now,” said Lina Khatib of the Paris-based Arab Reform Initiative think tank.

Peace talks scheduled to start in Geneva next week are already in doubt because of disputes between Russia and the United States, their chief sponsors, over who should be invited.